1. Field of the Invention
This invention relates to a machining center and more particularly to a pallet changing system for a machining center.
2. Background Art
Machining centers are used to machine workpieces in various operations to within precise tolerances. In order to meet such tolerances, workpieces have been clamped to pallets which are themselves clamped to the machining center. A pallet having a workpiece to be machined can then be moved (known as indexing) to properly orient it with respect to the cutting tool of the machining center.
Pallet changers have been provided for changing pallets in the machining position of a machining center. When the machining of one workpiece is completed, pallets are exchanged on the machining center so that the pallet with the finished workpiece is replaced by a pallet with a new workpiece. Then, while machining of the new workpiece occurs, the finished workpiece may be replaced on the other pallet by a new piece so that the pallets can again be exchanged to locate still another new workpiece for machining.
One type of pallet changer which has been used is a rotary type changer which extends to pick up the pallet at the machining position, retracts with the picked up pallet and rotates to present a new pallet, and then extends to place the new pallet in the machining position. Unfortunately, it has not been possible to fully protect the components of this type of changer from the metal shavings which are produced during the machining of a workpiece and which can interfere with the proper working of the pallet changer mechanism.
Another type of pallet changer which has been used shuttles two pallets back and forth over a track or tracks between a machining position and a standby position. Most of the pallet changers of this type have also not been properly protected from metal shavings. Those pallet changers which have used covers to protect the track have, however, required separate indexing mechanisms associated with each pallet. This unnecessary duplication of parts has resulted in an increased possibility of system failure or error and also in an undesirable increase in cost.
This invention is directed towards overcoming one or more of the problems as set forth above.